Silicon Valley's male elite are known to regularly throw lavish and exclusive sex parties with copious amounts of drugs and women, according to multiple insiders.

Bloomberg TV anchor Emily Chang has spent the past two years researching and writing her soon-to-be released book, which delves into the inner workings of the sex parties of the tech and famous.

The freewheeling sex culture that she details in Brotopia: Breaking Up the Boys' Club of Silicon Valley is said to be an open secret in high-flying tech circles but the vast majority are unaware of what goes on.

In an excerpt in Vanity Fair, Chang's book details Silicon Valley's sex culture as told to her by two dozen, mostly anonymous, people who have attended the parties.

They say that founders, investors and entrepreneurs - some of whom are well known - are known to host weekend-long parties where the ratio of women to men is about two to one.

The parties almost always include some form of MDMA, including some that have been shaped into the logos of major tech companies.

Before the drugs are rolled out, the parties often start with dinner and drinks. They end with group 'cuddle puddles', which ends up leading to sexual encounters - sometimes in groups of two and three.

They are held in various venues, including mansions in San Francisco's Pacific Heights or the wealth suburb of Atherton. Parties also take place in Napa Valley châteaus, beachfront home in Malibu or as far as yachts in Ibiza.

Chang says that many of the guests actually turn up with their wives, husbands or partners with open relationships supposedly becoming more common in tech circles.

The sex parties happen so often that they are commonly referred to as a lifestyle choice and they are not thought of as scandalous.

Women are not forced to attend but those that do participate are often stigmatized by Silicon Valley high-fliers and lose respect in the industry.

'If you do participate in these sex parties, don't ever think about starting a company or having someone invest in you. Those doors get shut. But if you don't participate, you're shut out. You're damned if you do, damned if you don't,' one female founder told Chang.

Another said: 'It's very hard to create a personal connection with a male investor, and if you succeed, they become attracted to you. They think you're part of their inner circle... in San Francisco that means you're invited to some kind of orgy. I couldn't escape it here.'

Chang writes that the male tech elite consider themselves more influential than actors and athletes.

'We have more cachet than a random rich dude because we make products that touch a lot of people,' one anonymous founder told Chang.

'You make a movie, and people watch it for a weekend. You make a product, and it touches people's lives for years.'

Some Silicon Valley men claim women are taking advantage of them because of their money. They say women become mysteriously more attracted to them no matter how uncool or unattractive they might be.

But the women who have dated them say it is the men who are obsessed with wealth. One woman said the men in question will take women on several extravagant dates before ditching them when it gets serious.

'They say, 'I'm still catching up. I lost my virginity when I was 25,' ' one woman said. 'And I'll say, 'Well, you're 33 now, are we all caught up yet?'

'In any other context, (these fancy dates) would be romantic, but instead it's charged because no one would f**k them in high school... I honestly think what they want is a do-over because women wouldn't bone them until now.'

The book's release comes at time when discrimination and sexual harassment allegations are being leveled at Silicon Valley men and companies.